Long-term outcomes and anorectal functional status of patients with anal squamous cell carcinoma treated with the modern technique of intensity-modulated radiotherapy

Intensity-modulated radiation therapy (IMRT) may reduce mortality in patients with squamous cell carcinoma of the anus (SCCA), but there are limited data in long-term outcomes. This study reported 5-year outcomes in SCCA patients treated with IMRT-based definitive chemoradiation. Sixty-five consecutive patients with T1-4N0-3M0 SCCA treated with IMRT-based concurrent chemoradiation (CCRT) from Jan 1, 2010, were retrospectively reviewed. Treatment outcomes included overall survival (OS), disease-free survival (DFS), anal cancer-specific mortality (ACSM), local-regional failure (LRF), distant metastasis (DM) and colostomy failure (CF), late toxicity and anorectal function. The patients had a median age of 52 years; 70.8% were female, 30.8% had T3-4 lesions, and 46.2% were clinically node positive. The median radiation doses to the gross tumor volume of the anus (GTVA) was 54 Gy (with a median BED10 of 65.7 Gy). The 5-year OS and DFS rates were 82.4% and 74.6%, respectively. The 5-year rates of ACSM, LRF, DM and CF were 13.9%, 18.0%, 6.5% and 19.0%, respectively. Patients treated with BED10 > 66 Gy exhibited inferior DFS and OS. The most common grade 3 late AEs were gastrointestinal (6.2%). The median Wexner score and Vaizey score were 0 and 2, respectively. The median LARS score was 0, with 3 patients reporting minor LARS. IMRT-based CCRT can achieve excellent long-term local control with manageable late toxicity in patients with locoregional SCCA. Anorectal function in long-term survivors was acceptable. Given different tumor burden, findings regarding radiation dose escalation beyond a BED10 of 66 Gy should be interpreted with caution.